/*
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You under the Apache License, Version 2.0
 *  (the "License"); you may not use this file except in compliance with
 *  the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 *
 */

/*
 * This package is based on the work done by Timothy Gerard Endres
 * (time@ice.com) to whom the Ant project is very grateful for his great code.
 */

package org.apache.tools.tar;

import java.io.FilterInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

/**
 * The TarInputStream reads a UNIX tar archive as an InputStream. methods are provided to position at each successive
 * entry in the archive, and the read each entry as a normal input stream using read().
 */
public class TarInputStream extends FilterInputStream{

    // CheckStyle:VisibilityModifier OFF - bc
    protected boolean   debug;
    protected boolean   hasHitEOF;
    protected long      entrySize;
    protected long      entryOffset;
    protected byte[]    readBuf;
    protected TarBuffer buffer;
    protected TarEntry  currEntry;

    /**
     * This contents of this array is not used at all in this class, it is only here to avoid repreated object creation
     * during calls to the no-arg read method.
     */
    protected byte[]    oneBuf;

    // CheckStyle:VisibilityModifier ON

    /**
     * Constructor for TarInputStream.
     * 
     * @param is
     *            the input stream to use
     */
    public TarInputStream(InputStream is){
        this(is, TarBuffer.DEFAULT_BLKSIZE, TarBuffer.DEFAULT_RCDSIZE);
    }

    /**
     * Constructor for TarInputStream.
     * 
     * @param is
     *            the input stream to use
     * @param blockSize
     *            the block size to use
     */
    public TarInputStream(InputStream is, int blockSize){
        this(is, blockSize, TarBuffer.DEFAULT_RCDSIZE);
    }

    /**
     * Constructor for TarInputStream.
     * 
     * @param is
     *            the input stream to use
     * @param blockSize
     *            the block size to use
     * @param recordSize
     *            the record size to use
     */
    public TarInputStream(InputStream is, int blockSize, int recordSize){
        super(is);

        buffer = new TarBuffer(is, blockSize, recordSize);
        readBuf = null;
        oneBuf = new byte[1];
        debug = false;
        hasHitEOF = false;
    }

    /**
     * Sets the debugging flag.
     * 
     * @param debug
     *            True to turn on debugging.
     */
    public void setDebug(boolean debug){
        this.debug = debug;
        buffer.setDebug(debug);
    }

    /**
     * Closes this stream. Calls the TarBuffer's close() method.
     * 
     * @throws IOException
     *             on error
     */
    @Override
    public void close() throws IOException{
        buffer.close();
    }

    /**
     * Get the record size being used by this stream's TarBuffer.
     * 
     * @return The TarBuffer record size.
     */
    public int getRecordSize(){
        return buffer.getRecordSize();
    }

    /**
     * Get the available data that can be read from the current entry in the archive. This does not indicate how much
     * data is left in the entire archive, only in the current entry. This value is determined from the entry's size
     * header field and the amount of data already read from the current entry. Integer.MAX_VALUE is returen in case
     * more than Integer.MAX_VALUE bytes are left in the current entry in the archive.
     * 
     * @return The number of available bytes for the current entry.
     * @throws IOException
     *             for signature
     */
    @Override
    public int available() throws IOException{
        if(entrySize - entryOffset > Integer.MAX_VALUE){
            return Integer.MAX_VALUE;
        }
        return (int)(entrySize - entryOffset);
    }

    /**
     * Skip bytes in the input buffer. This skips bytes in the current entry's data, not the entire archive, and will
     * stop at the end of the current entry's data if the number to skip extends beyond that point.
     * 
     * @param numToSkip
     *            The number of bytes to skip.
     * @return the number actually skipped
     * @throws IOException
     *             on error
     */
    @Override
    public long skip(long numToSkip) throws IOException{
        // REVIEW
        // This is horribly inefficient, but it ensures that we
        // properly skip over bytes via the TarBuffer...
        //
        byte[] skipBuf = new byte[8 * 1024];
        long skip = numToSkip;
        while(skip > 0){
            int realSkip = (int)(skip > skipBuf.length ? skipBuf.length : skip);
            int numRead = this.read(skipBuf, 0, realSkip);
            if(numRead == -1){
                break;
            }
            skip -= numRead;
        }
        return numToSkip - skip;
    }

    /**
     * Since we do not support marking just yet, we return false.
     * 
     * @return False.
     */
    @Override
    public boolean markSupported(){
        return false;
    }

    /**
     * Since we do not support marking just yet, we do nothing.
     * 
     * @param markLimit
     *            The limit to mark.
     */
    @Override
    public void mark(int markLimit){}

    /**
     * Since we do not support marking just yet, we do nothing.
     */
    @Override
    public void reset(){}

    /**
     * Get the next entry in this tar archive. This will skip over any remaining data in the current entry, if there is
     * one, and place the input stream at the header of the next entry, and read the header and instantiate a new
     * TarEntry from the header bytes and return that entry. If there are no more entries in the archive, null will be
     * returned to indicate that the end of the archive has been reached.
     * 
     * @return The next TarEntry in the archive, or null.
     * @throws IOException
     *             on error
     */
    public TarEntry getNextEntry() throws IOException{
        if(hasHitEOF){
            return null;
        }

        if(currEntry != null){
            long numToSkip = entrySize - entryOffset;

            if(debug){
                System.err.println("TarInputStream: SKIP currENTRY '"
                    + currEntry.getName() + "' SZ " + entrySize + " OFF "
                    + entryOffset + "  skipping " + numToSkip + " bytes");
            }

            if(numToSkip > 0){
                skip(numToSkip);
            }

            readBuf = null;
        }

        byte[] headerBuf = buffer.readRecord();

        if(headerBuf == null){
            if(debug){
                System.err.println("READ NULL RECORD");
            }
            hasHitEOF = true;
        }else if(buffer.isEOFRecord(headerBuf)){
            if(debug){
                System.err.println("READ EOF RECORD");
            }
            hasHitEOF = true;
        }

        if(hasHitEOF){
            currEntry = null;
        }else{
            currEntry = new TarEntry(headerBuf);

            if(debug){
                System.err.println("TarInputStream: SET CURRENTRY '"
                    + currEntry.getName() + "' size = " + currEntry.getSize());
            }

            entryOffset = 0;

            entrySize = currEntry.getSize();
        }

        if(currEntry != null && currEntry.isGNULongNameEntry()){
            // read in the name
            StringBuffer longName = new StringBuffer();
            byte[] buf = new byte[256];
            int length = 0;
            while((length = read(buf)) >= 0){
                longName.append(new String(buf, 0, length));
            }
            getNextEntry();
            if(currEntry == null){
                // Bugzilla: 40334
                // Malformed tar file - long entry name not followed by entry
                return null;
            }
            // remove trailing null terminator
            if(longName.length() > 0
                && longName.charAt(longName.length() - 1) == 0){
                longName.deleteCharAt(longName.length() - 1);
            }
            currEntry.setName(longName.toString());
        }

        return currEntry;
    }

    /**
     * Reads a byte from the current tar archive entry. This method simply calls read( byte[], int, int ).
     * 
     * @return The byte read, or -1 at EOF.
     * @throws IOException
     *             on error
     */
    @Override
    public int read() throws IOException{
        int num = this.read(oneBuf, 0, 1);
        return num == -1 ? -1 : oneBuf[0] & 0xFF;
    }

    /**
     * Reads bytes from the current tar archive entry. This method is aware of the boundaries of the current entry in
     * the archive and will deal with them as if they were this stream's start and EOF.
     * 
     * @param buf
     *            The buffer into which to place bytes read.
     * @param offset
     *            The offset at which to place bytes read.
     * @param numToRead
     *            The number of bytes to read.
     * @return The number of bytes read, or -1 at EOF.
     * @throws IOException
     *             on error
     */
    @Override
    public int read(byte[] buf, int offset, int numToRead) throws IOException{
        int totalRead = 0;

        if(entryOffset >= entrySize){
            return -1;
        }

        if(numToRead + entryOffset > entrySize){
            numToRead = (int)(entrySize - entryOffset);
        }

        if(readBuf != null){
            int sz = numToRead > readBuf.length ? readBuf.length : numToRead;

            System.arraycopy(readBuf, 0, buf, offset, sz);

            if(sz >= readBuf.length){
                readBuf = null;
            }else{
                int newLen = readBuf.length - sz;
                byte[] newBuf = new byte[newLen];

                System.arraycopy(readBuf, sz, newBuf, 0, newLen);

                readBuf = newBuf;
            }

            totalRead += sz;
            numToRead -= sz;
            offset += sz;
        }

        while(numToRead > 0){
            byte[] rec = buffer.readRecord();

            if(rec == null){
                // Unexpected EOF!
                throw new IOException("unexpected EOF with " + numToRead
                    + " bytes unread");
            }

            int sz = numToRead;
            int recLen = rec.length;

            if(recLen > sz){
                System.arraycopy(rec, 0, buf, offset, sz);

                readBuf = new byte[recLen - sz];

                System.arraycopy(rec, sz, readBuf, 0, recLen - sz);
            }else{
                sz = recLen;

                System.arraycopy(rec, 0, buf, offset, recLen);
            }

            totalRead += sz;
            numToRead -= sz;
            offset += sz;
        }

        entryOffset += totalRead;

        return totalRead;
    }

    /**
     * Copies the contents of the current tar archive entry directly into an output stream.
     * 
     * @param out
     *            The OutputStream into which to write the entry's data.
     * @throws IOException
     *             on error
     */
    public void copyEntryContents(OutputStream out) throws IOException{
        byte[] buf = new byte[32 * 1024];

        while(true){
            int numRead = this.read(buf, 0, buf.length);

            if(numRead == -1){
                break;
            }

            out.write(buf, 0, numRead);
        }
    }
}
